Product Overview
Reliable custom rubber parts for industrial applications
Quick Answer
Green FKM low-temp grade O-rings are molded fluoroelastomer seals for industrial sealing applications requiring FKM-type resistance with improved low-temperature flexibility. Multiple sizes, inner diameters, cross-sections, Shore A hardness levels, tolerances, packaging formats and documentation options can be customized according to drawings, size lists or samples.
Green FKM Low-Temperature O-Rings — GLT / GFLT Fluorocarbon Grade, -40°C to +200°C, All Sizes
Green FKM low-temp grade O-rings are molded fluoroelastomer seals designed for groove-based sealing where oil, fuel, chemical exposure and lower-temperature flexibility must be considered together. They are available in multiple inner diameters and cross-sections. Size range, Shore A hardness, dimensional tolerance, packaging and documentation can be customized according to drawings or application requirements.
Product Overview
Green FKM low-temp grade O-rings are circular elastomer seals with a round cross-section. They are installed in grooves and compressed between mating components to form static or selected dynamic seals. Compared with standard FKM grades, low-temp grade FKM can be reviewed when the application requires improved flexibility at lower operating temperatures while retaining FKM’s typical resistance to oils, fuels and selected chemical media. The green color supports material identification during storage, assembly and maintenance. Multiple sizes can be supplied according to standard references, customer drawings, equipment service lists or physical samples. Final performance depends on groove design, squeeze rate, pressure, media, temperature and compound grade.
| Attribute | Value |
|---|---|
| Product Name | Green FKM Low-Temperature Grade O-Ring |
| Material | FKM GLT / GFLT — Low-Temperature Fluorocarbon Elastomer |
| Also Known As | Viton® GLT O-Ring; FPM Green O-Ring; Low-Temp Fluororubber O-Ring |
| Color | Green (standard low-temp FKM identification color) |
| Hardness | Shore A 70–75 (standard); 60A, 80A available |
| Standard Series | AS568A Imperial; ISO 3601 Metric; DIN 3771; BS 1806 |
| CS Range | 1.0 mm to 10.0 mm |
| ID Range | 1.5 mm to 400 mm standard; larger lathe-cut on request |
| Temperature Range | -40°C to +200°C (GLT); -55°C to +200°C (GFLT) |
| Pressure Rating | Static: up to 200 bar (with back-up rings); Dynamic: up to 80 bar |
| Fabrication | Compression moulding; lathe-cut (large diameter) |
| Certifications | RoHS; REACH; AMS7410 (aerospace GFLT); MIL-R-83485 GLT-type available |
Why Green? — The Low-Temp FKM Color Convention
Green is the universally adopted color code specifically for low-temperature FKM O-rings — distinguishing them from standard brown FKM 75A in maintenance environments where the temperature capability difference is operationally critical.
In press-fitting systems, HVAC, and industrial piping, green immediately signals FKM compound with extended cold-temperature performance:
| Color | Compound | Temp Range | Key Application |
|---|---|---|---|
| Black | NBR | -40°C to +100°C | Oil, hydraulic fluid |
| Black | EPDM | -50°C to +150°C | Water, steam |
| Green | FKM GLT / GFLT | -40°C to +200°C | Cold climate + chemical |
| Brown | FKM Standard | -20°C to +200°C | Chemical, fuel, hot oil |
| Red | VMQ Silicone | -60°C to +250°C | High temp, FDA |
| Green | FKM (press-fit) | -20°C to +180°C | Solar thermal, oil circuits |
The green color prevents the critical installation error of using standard brown FKM (-20°C limit) in outdoor or cold-climate installations where ambient temperatures routinely drop below -20°C — a mistake that causes brittle fracture of the O-ring at first cold-weather pressurization.
FKM GLT vs. GFLT vs. Standard FKM — Grade Comparison
Three distinct FKM grades are available for different temperature-performance requirements:
| Grade | Color | Fluorine Content | Lower Temp | Upper Temp | Chemical Resistance | Cost |
|---|---|---|---|---|---|---|
| FKM Standard (Type 1) | Brown | 66% F | -20°C | +200°C | Outstanding | Medium |
| FKM GLT | Green | 64–66% F + modifier | -40°C | +200°C | Outstanding | Medium-High |
| FKM GFLT | Green / Black | 60–64% F + perfluoro | -55°C | +200°C | Outstanding | High |
| FKM Extreme LT (AMS7410) | Black | Modified | -65°C | +200°C | Excellent | Very High |
GLT (General Low Temperature) — the standard green FKM grade for most cold-climate industrial applications. Achieves -40°C flexibility through incorporation of perfluoromethylvinylether (PMVE) or propylene-modified polymer backbone. Retains full FKM chemical resistance spectrum.
GFLT (Grade for Low Temperature) — the premium green FKM grade for the most demanding cold-temperature applications. Higher PMVE content extends the flexibility limit to -55°C; specified in LNG facilities, Arctic oil and gas installations, and aerospace fuel system O-rings to AMS7410.
Key Physical Properties (Green FKM GLT Shore A 70)
| Property | Test Method | Value |
|---|---|---|
| Hardness | ISO 48-4 / Shore A | 70 ± 5 |
| Tensile Strength | ISO 37 | ≥ 9 MPa |
| Elongation at Break | ISO 37 | ≥ 175% |
| Compression Set | ISO 815 (22h @ 175°C) | ≤ 22% |
| Compression Set | ISO 815 (22h @ -40°C) | ≤ 30% |
| Volume Change in Oil | ISO 1817 (IRM 903, 70h @ 150°C) | ≤ +8% |
| Heat Aging | ISO 188 (70h @ 200°C) | ≤ ±15% |
| Low-Temp Flexibility (TR10) | ISO 812 | ≤ -35°C (GLT) |
| Low-Temp Flexibility (TR10) | ISO 812 | ≤ -48°C (GFLT) |
| Density | ISO 2781 | 1.75–1.90 g/cm³ |
| Temperature Range (GLT) | Continuous | -40°C to +200°C |
| Temperature Range (GFLT) | Continuous | -55°C to +200°C |
Standard Size Reference Tables
ISO 3601 Metric — Green FKM GLT 70A (Selected Sizes)
| ID (mm) | CS (mm) | OD (mm) | ISO Designation |
|---|---|---|---|
| 3.0 | 1.5 | 6.0 | G3 |
| 5.0 | 1.5 | 8.0 | G5 |
| 8.0 | 1.5 | 11.0 | G8 |
| 10.0 | 2.0 | 14.0 | G10 |
| 12.0 | 2.0 | 16.0 | G12 |
| 15.0 | 2.5 | 20.0 | G15 |
| 20.0 | 2.5 | 25.0 | G20 |
| 25.0 | 3.0 | 31.0 | G25 |
| 30.0 | 3.0 | 36.0 | G30 |
| 40.0 | 3.5 | 47.0 | G40 |
| 50.0 | 4.0 | 58.0 | G50 |
| 75.0 | 5.0 | 85.0 | G75 |
| 100.0 | 5.0 | 110.0 | G100 |
| 150.0 | 6.0 | 162.0 | G150 |
| 179.3 | 5.7 | 190.7 | G180 (press-fit) |
| 200.0 | 7.0 | 214.0 | G200 |
Chemical Resistance — Same as Standard FKM, Extended Temperature
Green FKM GLT/GFLT retains the full chemical resistance spectrum of standard FKM — the low-temperature modification changes the polymer’s flexibility at cold temperatures but does not compromise its chemical resistance:
| Chemical Class | Examples | Green FKM Rating |
|---|---|---|
| Petroleum oils | Mineral oil, gear oil, hydraulic oil | ✅ Excellent |
| Synthetic hydraulic fluid | Phosphate ester (Skydrol), polyol ester | ✅ Excellent |
| Aliphatic fuels | Petrol, diesel, kerosene, LPG | ✅ Excellent |
| Aromatic hydrocarbons | Benzene, toluene, xylene | ✅ Excellent |
| Chlorinated solvents | Trichloroethylene, CCl₄ | ✅ Excellent |
| Concentrated acids | H₂SO₄, HNO₃ (dilute-moderate) | ✅ Good |
| Biodiesel blends | B20–B100 | ✅ Good |
| Ozone / UV / weathering | Outdoor atmospheric | ✅ Excellent |
| High vacuum | ≤ 10⁻⁷ Torr | ✅ Excellent |
| NOT suitable for: | Ketones, esters, amines, hot steam >120°C | ❌ Avoid |
Primary Application Markets
Outdoor & Cold-Climate Industrial Equipment
The defining application for green FKM O-rings. Any outdoor industrial installation in cold climate regions — northern Europe, Canada, Siberia, high-altitude facilities — where ambient temperatures routinely fall below -20°C requires O-rings that remain flexible and maintain sealing contact stress at low temperature. Standard brown FKM becomes too stiff below -20°C and loses sealing contact stress; green FKM GLT maintains full elastic functionality to -40°C, preventing cold-weather leak events at system start-up.
Solar Thermal Systems
Green FKM is the standard O-ring specification for solar thermal collector systems — particularly high-temperature flat-plate and evacuated-tube collector circuits. Solar thermal circuits combine high operating temperatures (+160°C to +180°C) with outdoor installation (ozone, UV, freeze-thaw cycling) and heat-transfer fluid media (glycol/water or synthetic heat-transfer oils) that exceed EPDM’s media compatibility. Green FKM press-fit O-rings in DN12–DN108 are the industry standard for solar circuit press-fitting connections.
Oil & Gas — Arctic and Cold-Climate Installations
Subsea equipment, Arctic pipeline connections, and cold-climate oilfield wellhead components require O-ring compounds that withstand crude oil, H₂S-containing produced water, and methanol injection fluids at temperatures as low as -40°C seabed temperature. Green FKM GLT covers this combined low-temperature and chemical resistance requirement; GFLT grade is specified for the most extreme cold-climate oilfield applications.
Aerospace — Fuel Systems (AMS7410 / MIL-R-83485)
Military and commercial aerospace fuel system O-rings must seal aviation gasoline, jet fuel (Jet A, JP-4, JP-8), and hydraulic fluid at both cruise altitude temperatures (-40°C to -55°C) and ground operating temperatures. Green and black FKM GFLT grade to AMS7410 and MIL-R-83485 is the mandated specification for aerospace fuel system O-rings requiring both chemical resistance and low-temperature performance.
Automotive — Cold-Start and Underhood Cold-Climate Applications
Turbocharger intercooler connections, fuel rail seals, and transmission fluid connections in vehicles operating in cold climates experience thermal cycling from -40°C cold-start to +150°C+ sustained operating temperature — a 190°C+ swing that standard brown FKM cannot fully cover at the cold end. Green FKM GLT 70A is the correct specification for underhood O-rings in cold-climate automotive applications.
Refrigeration & HVAC — Cold Side Connections
Industrial refrigeration systems with evaporator connections operating at low suction pressures and temperatures (-30°C to -40°C refrigerant temperatures), combined with synthetic refrigeration oil contact, require O-ring compounds with simultaneous low-temperature flexibility and oil resistance. Green FKM GLT uniquely provides both.
Chemical Process — Low-Temperature Chemical Service
Chemical process plants handling aromatic solvents, chlorinated solvents, and liquid hydrocarbons at low process temperatures (cryogenic fractionation, LNG processing) require O-ring compounds with both chemical resistance and low-temperature flexibility. Green FKM GFLT covers chemical process O-ring applications down to -55°C.
Green FKM vs. Competing Low-Temperature Compounds
When an application requires both chemical resistance and low-temperature performance, green FKM GLT/GFLT is typically the only standard compound covering both requirements simultaneously:
| Compound | Min Temp | Chemical Resistance | Oil Resistance | Cost |
|---|---|---|---|---|
| Green FKM GLT | -40°C | Outstanding | Excellent | Medium-High |
| Green FKM GFLT | -55°C | Outstanding | Excellent | High |
| NBR Low-Temp | -55°C | Moderate | Good | Low |
| VMQ Silicone | -60°C | Good | Poor | Medium |
| HNBR | -40°C | Good | Excellent | Medium |
| EPDM | -50°C | Good (water only) | Poor | Low |
| FFKM | -20°C | Universal | Excellent | Very High |
Key advantage over NBR Low-Temp: NBR low-temp achieves low-temperature flexibility but cannot handle aromatic solvents, concentrated chemicals, or temperatures above +100°C. Green FKM covers all of these simultaneously.
Key advantage over VMQ Silicone: VMQ achieves lower temperature flexibility but has poor oil and fuel resistance. Green FKM covers oil, fuel, and chemical contact while matching VMQ’s cold temperature performance down to -40°C (GLT) or -55°C (GFLT).
Press-Fitting System Application — Green FKM for Solar & Oil Circuits
In the press-fitting piping system market — Viega, Geberit, Watts, and equivalent press-fit connection systems — green FKM O-rings are the standard specification for:
- Solar thermal circuits (glycol/water heat transfer fluid, +160°C to +180°C)
- Oil and hydrocarbon circuits (mineral oil, synthetic oil)
- High-temperature heating circuits above EPDM’s +120°C practical limit
- Industrial compressed air with residual oil > 5 mg/m³
Press-fit green FKM O-rings are available in standard press-fitting sizes:
| Press-Fit DN | OD (mm) | Green FKM Grade |
|---|---|---|
| 12 | 15.0 | GLT |
| 15 | 18.0 | GLT |
| 18 | 22.0 | GLT |
| 22 | 28.0 | GLT |
| 28 | 35.0 | GLT |
| 35 | 42.0 | GLT |
| 42 | 54.0 | GLT |
| 54 | 66.8 | GLT |
| 76.1 | 88.9 | GLT |
| 88.9 | 108.0 | GLT |
Groove Design Reference — Green FKM GLT 70A
Green FKM GLT at Shore A 70 uses identical groove geometry to standard FKM and NBR per AS568A and ISO 3601 groove standards:
| Application | Recommended Squeeze | Surface Finish (Ra) | Notes |
|---|---|---|---|
| Static face seal | 20–27% | ≤ 3.2 μm | Standard industrial |
| Static radial | 18–24% | ≤ 3.2 μm | Standard industrial |
| Dynamic reciprocating | 12–18% | 0.2–0.4 μm | Lubricate; FKM-compatible grease |
| Dynamic rotary | 10–15% | 0.2–0.4 μm | ≤ 0.5 m/s surface speed |
| High pressure (>100 bar) | 20–25% | ≤ 1.6 μm | Add PTFE back-up ring |
Installation Best Practices — Green FKM Specific
- Cold environment installation — even GLT grade becomes noticeably stiffer below -10°C; warm O-rings to +15°C before installation in cold ambient conditions to restore flexibility and prevent tearing during fitting
- FKM-compatible lubricant only — use petroleum jelly, mineral grease, or silicone grease; never use ketone-based, ester-based, or amine-based lubricants which swell FKM
- Visual identification verification — confirm green color before installation; in mixed-compound kits, green = FKM low-temp grade; do not install in steam service or hot water service above +120°C where EPDM is required
- Protect from sharp bore edges — use installation sleeves on threaded or grooved bores; FKM at 70–75A is less flexible than NBR during installation
- Allow thermal conditioning — in solar thermal and high-temperature applications, bring system to operating temperature gradually at first pressurization; inspect all press-fit and O-ring connections before full operating load
Storage & Shelf Life
| Parameter | Green FKM GLT Guidance |
|---|---|
| Shelf life | 10+ years from manufacture (ISO 2230) |
| Storage temperature | +15°C to +25°C |
| Packaging | Original sealed poly bags; compartmentalized storage |
| Ozone / UV | FKM is inherently ozone-resistant; standard indoor storage applies |
| Segregation | Store separately from NR, SBR compounds — fluoroelastomers can absorb volatile plasticizers from natural rubber |
Quality & Compliance
| Standard | Status |
|---|---|
| AS568A dimensional | ✅ Full range |
| ISO 3601 dimensional | ✅ Full metric range |
| Hardness ISO 48-4 | ✅ Shore A 70 ± 5 |
| Compression Set ISO 815 | ✅ ≤ 22% (22h @ 175°C) |
| Low-temp TR10 ISO 812 | ✅ ≤ -35°C (GLT); ≤ -48°C (GFLT) |
| AMS7410 | ✅ GFLT grade — aerospace extreme LT FKM |
| MIL-R-83485 GLT | ✅ Available for aerospace supply |
| RoHS 2011/65/EU | ✅ Compliant |
| REACH 1907/2006 | ✅ Compliant |
| AS9100 Rev D | ✅ Available for aerospace supply |
| EN 10204 Type 3.1 | ✅ Full material certificate on request |
FAQ
What are green FKM low-temp grade O-rings used for?
Green FKM low-temp grade O-rings are used for sealing applications where oil, fuel, selected chemical exposure and lower-temperature flexibility must be reviewed together. They are commonly installed in grooves for pumps, valves, connectors, fuel-system parts, instruments and industrial equipment.
How is low-temp grade FKM different from standard FKM?
Low-temp grade FKM is selected when the application requires improved flexibility at lower temperatures compared with standard FKM grades. Exact performance depends on the compound formulation, hardness, media exposure and sealing design. Buyers should confirm the minimum operating temperature before material approval.
Why are these FKM O-rings green?
Green is often used for visual identification in sealing programs. It helps warehouse staff, assemblers and maintenance teams distinguish the O-ring material or grade from black NBR, EPDM or standard FKM seals. Color should not replace material verification for critical applications.
Can the O-rings be supplied in multiple sizes?
Yes. Multiple inner diameters and cross-sections can be supplied according to a size list, standard reference, drawing or physical sample. Buyers should provide the required quantity for each size and identify whether the parts are for production assembly, MRO kits or distributor assortment supply.
Is FKM suitable for all chemicals and fuels?
No. FKM provides strong resistance to many oils, fuels and selected chemicals, but it is not compatible with every media. Buyers should provide the exact media name, concentration, temperature and exposure condition so the FKM grade can be reviewed before production.
Are samples available before bulk production?
Samples are available upon request. Sample planning depends on the O-ring sizes, compound grade, Shore A hardness, tolerance, tooling status, packaging method and quantity. Please provide a size list, drawing or physical sample for technical review.
Request a Custom Quote
Send your green FKM low-temp grade O-ring size list, drawing, standard reference or physical sample for review. Please include ID, cross-section, quantity per size, hardness, contact media, temperature range, pressure, sealing condition, groove dimensions, packaging method and documentation requirements.
